The overall objective of this Program Project is to provide new and fundamental information on how nature controls mineralization in developing mineralized tissues, like enamel, using amelogenesis as a model. Our overall working hypothesis is that the formation of the highly organized enamel tissue results from genetically-controlled processes involving: cell motility, mineral ion fluxes; the secretion, self assembly and processing of matrix proteins, and the subsequent control of nucleation and crystal growth by specialized proteins coupled with the cell-controlled establishment of inherent driving forces to support mineralization. Specifically, we propose to elucidate fundamental mechanisms which control enamel formation through integrated studies on: 1). matrix protein-mineral interactions in the control of crystal nucleation and crystal growth; 2) the cellular (ameloblast) control of mineral ion transport, extracellular mineral ion composition, pH. and the driving force for mineral deposition; 3) the role of specific protein-protein interactions in the control of mineralization; 4) the control of protein function and mineralization via the processing of enamel-matrix proteins by tissue-specific proteinases; and 5) cell (ameloblast)-cell interactions and cell-matrix interactions, leading to the control of cell motility and enamel patterning. These studies will be carried out through the integration of five independent projects facilitated by a Protein Core, which will generate recombinant enamel proteins in both bacteria and eukaryotic cell expression systems. These areas of research will be addressed in a multi-disciplinary fashion using state-of-the-art techniques (e.g. the yeast two-hybrid system; PCR-based homology cloning, atomic force microscopy, confocal microscopy and direct 3-D fluorescence microscopy; SEM and TEM; immunohistochemistry) and physiochemical considerations to address the overall mechanisms of enamel formation. Long term, this information will be useful in: 1) the design of new methodologies for the preparation of biomaterials with specific desirable properties; 2) the diagnosis and prevention of diseases mineralized tissues through genetic means; and 3) the design of procedures for the regeneration of damaged and diseases mineralized tissues.